1. Field of the Invention
This invention relates to a photosensitive member for use in electrophotography.
2. Description of the Prior Art
The electrophotographic photosensitive member takes various constructions for obtaining a predetermined characteristics or in accordance with the kind of the electrophotographic processes to be applied. Representative photosensitive member for the electrophotography is such one that is provided with a photoconductive layer on a substrate or such one that is provided with an insulating layer on the surface of the photoconductive layer, both types being used widely. The photosensitive member consisting of the substrate and the photoconductive layer is used for image formation by the most common electrophotographic processes including electric charging, image exposure, image development, and, depending on necessity, image transfer. As to the photosensitive member having the insulative layer thereon, such insulative layer is provided for the purposes of protecting the photoconductive layer, improving the mechanical strength of the photosensitive member, improving the dark decay characteristic, or being applied to a particular electrophotographic process, or further preventing pollutions. Representative examples of the photosensitive member having such insulative layer and the electrophotographic process using the photosensitive body having such insulative layer thereon are disclosed, for example, in U.S. Pat. No. 2,860,048, Japanese patent publications Nos. 16429/1966, 15446/1963, 3713/1971, 23910/1967, 24748/1968, 19747/1967, 4121/1961, and so on.
The electrophotographic photosensitive member is liable to be damaged inasmuch as it is subjected to various electrical and mechanical impacts such as corona charging process, image developing process, cleaning process, and so forth. It is also liable to lower its charge sustaining capability on account of moisture. Therefore, when the electrophotographic photosensitive member undergoes such damages time and again, the quality of the image to be formed thereon becomes remarkably deteriorated. In particular, when the photoconductive layer is composed of a binder and a photoconductive material (various resins being used as the binder), its durability is also poor. Also, the image to be formed on the electrophotographic photosensitive member is poorer in its tonality than the image formed by use of ordinary photographic emulsion.
In the photosensitive member having the insulative layer, when the layer is formed on the photoconductive layer, it becomes necessary for the photosensitive member to be excellent in its durability so that the insulative layer of a desired mechanical strength may be formed thereon without disturbing the composition of the photoconductive layer. For this purpose, when the insulative layer is formed by, for example, application of a liquid resin, the photoconductive layer should not be of such quality that is dissolved in the solvent of the liquid resin.
In view of the foregoing, there has so far been strong demands for the electrophotographic photosensitive member excellent in durability against electrical and mechanical impacts, moisture resistance, tonality, and so forth. However, it has been difficult to provide such electrophotographic photosensitive member excellent in these various characteristics.